This application claims priority from and incorporates by reference the subject matter of Swiss Patent Application No. 2000 2396/00 filed Dec. 6, 2000.
The invention concerns a Die Bonder and/or Wire Bonder with a device for holding down a substrate.
When mounting semiconductor chips onto a substrate by means of a so-called Die Bonder, the substrate is transported in cycles on a support surface by a predetermined distance in a transport direction and/or laterally to the transport direction so that a semiconductor chip can be mounted in the foreseen position. With the Die Bonders marketed by the applicant, the substrate lies on a rigidly arranged plate which has a drill hole which can be connected to a vacuum source for sucking and holding down the substrate. For the processing of so-called matrix substrates with which the chip islands for accepting the semiconductor chips are arranged in rows and columns, a downholder device with only one drill hole is hardly suitable: When mounting the semiconductor chips, one chip island after the other has to be transported to the rigidly arranged drill hole. In doing so, undesirable abrasion marks can occur on the underneath of the matrix substrate.
Die Bonders are also known with which the matrix substrate lies on a plate with several drill holes which moves together with the matrix substrate when movement of the matrix substrate at right angles to transport direction is necessary. For matrix substrates with cut-outs, with which the chip islands are separated from each other, a plate must be manufactured for each type of substrate the drill holes of which are adapted to the geometry of the chip islands.
The object of the invention is to develop a downholder device which is suitable for substrates of different types and geometry.
A device in accordance with the invention has a table for holding down the substrate. The table contains a connection to which vacuum can be applied as well as drill holes which run at right angles to the transport direction of the substrate. In a mechanical way it can be programmed which of the drill holes are connected to the vacuum connection and which of the drill holes are not connected to the vacuum connection.
With a first embodiment, the drill holes open out onto a groove covered by a foil which is connected to the vacuum connection in the table. By piercing the foil by means of a point in that the point is pushed into individually selected drill holes it is possible to manually determine which of the drill holes are in contact with the groove and therefore carry vacuum when vacuum is applied to the groove. The groove is incorporated into a drawer removably arranged in the table so that the foil can be exchanged in an easy manner.
With a second embodiment, an under surface of the table has several, but at least two, cavities of differing length which are connected to the vacuum connection. The table contains a removable drawer which can be engaged in various positions. The side of the drawer facing the under surface of the table contains cavities which form channels which connect the vacuum carrying cavity in the table with individual drill holes. The number of these channels is dependent on the actual engaging position of the drawer. In position 1 of the drawer, only one channel is present, in position 2 of the drawer two channels are present, etc. In this way, by shifting the position of the drawer it is possible to change the distance between the outermost drill holes which carry vacuum.